I have just started my new project which is a Freedom 17. This canoe will be used on flat water for day trips and for canoe camping outings. The plan says that the weight is from 45 to 55 pounds.
I am after some advice on how to build it at 45 pound or less without sacrificing the integrity and the rigidity of the hull.
After putting some thought into it I have concluded that 1/4 inch planks and 6 ounces fiberglass will drive the weight right up. I am presently planning to use 3/16 inch planks and 6 ounces fiberglass on the outside and 4 ounces on the inside but I am unsure of the results. Has anyone tried this approach and was it ok?
Additionally, what are the other strategies to reduce weight without underbuilding it?
Building a light Freedom 17
thickness/weight
I do believe that thinner strips will give you a weaker hull. It is the thickness of the sandwich that give it the stiffness. That 1/16th inch of cedar weighs very little. Also it is the inside laminate that gives the hull strenght against a stress from the outside. I would not skimp on the inside glass. Instead consider a below waterline/ above waterline difference in layup. For the inside I use 4 ounce cloth double to the waterline. Two pieces, each go from the gunwale on one side to just above the waterline on the other. I usually do the same on the outside. I think two pieces of 4oz over lapped a few inches at the keel and then a piece of 3.2oz satin weave covering the bottom on the outside might make a lighter hull with good strength and abrasion resistance. You need to make sure that the break between one layer and two are not in the same place for the inside and outside laminates. this would cause an abrupt change in strength and stiffness that would lead to failure under stress at that point. Stagger them a few inches. If you are going to make a lighter hull you need be experimenting with some of the lighter weight and denser fabrics available.
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Juneaudave
- Posts: 522
- Joined: Sat May 08, 2004 12:42 pm
- Location: Juneau, Alaska
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François...Boy have you opened up a topic on this board!!! It was discussed without end on the old board and I'm sure you will get some good ideas here.
One Idea I like is the thought of using a lighter weight outer gunnel material with an edge of a durable hardwood glued to the outside. Don't know how much it saves but it sounds good.
Might try maximizing scupper length on the inside.
Decks can be built in a number of minimalist ways without sacrificing strength.
One Idea I like is the thought of using a lighter weight outer gunnel material with an edge of a durable hardwood glued to the outside. Don't know how much it saves but it sounds good.
Might try maximizing scupper length on the inside.
Decks can be built in a number of minimalist ways without sacrificing strength.
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Todd Bradshaw
- Posts: 92
- Joined: Tue May 11, 2004 8:16 pm
3/16" strips work just fine with a decent glass layup on anything up to 20' long. I've used big tripping boats and racing boats built with 3/16" strips for 30 years and have had no problems. There are even builders who go all the way down to 1/8" strips and make up for the difference with exotic fiberglass layups to produce light boats with reasonable durability. I don't know what the difference in actual strength is if you set out with a hammer to destroy a boat, but in normal use - including an occasional unexpected impact with a submerged rock, you should be fine.
I just wrote a reply on the "reverse rocker" thread about something that caught my eye along the way and then thought maybe it was too far off topic or none of my business and deleted it, but here it is again and it's obvious that many people don't understand it. With the layup that you are proposing, you might as well use 4 oz. cloth inside and out, because your proposal to use 6 oz. outside and 4 oz. inside adds little if anything to the boat other than excess weight. You aren't getting any benefit from the heavier glass on the outside and the boat.
Strippers are sandwich constructions. The sum of their parts is much stronger and more rigid than the individual parts would be. Reducing one half of the "bread" (the glass on your sandwich) just makes the whole construction weaker - especially if it's the inside that's being reduced. Whether you happen to hit a rock or the boat is just sitting loaded in the water, the outside layers of the sandwich are mostly in compression and the inside layers are in tension. Upon impact, or when the bottom bounces, the outside deflects a little and the inside deflects a lot more. If the inside isn't up to the task, it tears, delaminates or both and often also splits strip-to-strip glue joints in the process. This effect is strong enough that even on regular, un-cored fiberglass canoes and kayaks, which may only have a few milimeters of total thickness, impacts usually damage the inside glass layers before, and more than, the outside. In the case of a stripper, the core is spacing them farther apart and compounding the problem. As a result, you are proposing a stripper hull which has most of the weight of a six-ounce layup, but the strength of a four-ounce layup.
Unless you have specifically tested an unbalanced layup to see that it meets your needs and holds-up for the long run, you're almost always better off balancing the inside and outside glass layers. Otherwise, you're likely to eventually need to start one of those "My canoe split between strips on the inside" or "the bottom of my canoe bounces like crazy" threads trying to find a fix.
I have always doubled-up the bottom layers, but only on the bottom and not up to the waterline. Once you get to the rounder part of the bilge the boat is so stiff just from curvature that I don't believe glassing farther up is going to make much difference in durability. If you actually did hit something in that chine area an extra layer of cloth running up to the waterline isn't going to do enough to offer much help.
For a light boat I'd go 3/16" strips, 4 oz. cloth inside and out and doubled on the bottom inside and out if you're willing to baby the boat or six ounce if you want more practical durability (the weight difference isn't all that much). A big portion of a canoe's weight is the trim. If you've ever seen a professionally-built marathon racer, like a Jensen, you can't help but notice that there is very little trim on the boat. Gunwales, seats and thwarts are all built very lightly and make up a big portion of the boats super lightweight nature.
I just wrote a reply on the "reverse rocker" thread about something that caught my eye along the way and then thought maybe it was too far off topic or none of my business and deleted it, but here it is again and it's obvious that many people don't understand it. With the layup that you are proposing, you might as well use 4 oz. cloth inside and out, because your proposal to use 6 oz. outside and 4 oz. inside adds little if anything to the boat other than excess weight. You aren't getting any benefit from the heavier glass on the outside and the boat.
Strippers are sandwich constructions. The sum of their parts is much stronger and more rigid than the individual parts would be. Reducing one half of the "bread" (the glass on your sandwich) just makes the whole construction weaker - especially if it's the inside that's being reduced. Whether you happen to hit a rock or the boat is just sitting loaded in the water, the outside layers of the sandwich are mostly in compression and the inside layers are in tension. Upon impact, or when the bottom bounces, the outside deflects a little and the inside deflects a lot more. If the inside isn't up to the task, it tears, delaminates or both and often also splits strip-to-strip glue joints in the process. This effect is strong enough that even on regular, un-cored fiberglass canoes and kayaks, which may only have a few milimeters of total thickness, impacts usually damage the inside glass layers before, and more than, the outside. In the case of a stripper, the core is spacing them farther apart and compounding the problem. As a result, you are proposing a stripper hull which has most of the weight of a six-ounce layup, but the strength of a four-ounce layup.
Unless you have specifically tested an unbalanced layup to see that it meets your needs and holds-up for the long run, you're almost always better off balancing the inside and outside glass layers. Otherwise, you're likely to eventually need to start one of those "My canoe split between strips on the inside" or "the bottom of my canoe bounces like crazy" threads trying to find a fix.
I have always doubled-up the bottom layers, but only on the bottom and not up to the waterline. Once you get to the rounder part of the bilge the boat is so stiff just from curvature that I don't believe glassing farther up is going to make much difference in durability. If you actually did hit something in that chine area an extra layer of cloth running up to the waterline isn't going to do enough to offer much help.
For a light boat I'd go 3/16" strips, 4 oz. cloth inside and out and doubled on the bottom inside and out if you're willing to baby the boat or six ounce if you want more practical durability (the weight difference isn't all that much). A big portion of a canoe's weight is the trim. If you've ever seen a professionally-built marathon racer, like a Jensen, you can't help but notice that there is very little trim on the boat. Gunwales, seats and thwarts are all built very lightly and make up a big portion of the boats super lightweight nature.
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Glen Smith
- Posts: 3719
- Joined: Sat May 08, 2004 9:08 am
- Location: Baie-St-Paul, Quebec, Canada
Hello Francios,
I'd go for the 3/16 strips. I haven't used them yet, I'll be doing so on my second boat - but I have made the calculations. I'm just finishing a winisk with a total square footage of planking at 65 square feet. (the Freedom for all intents and purposes should be about the same). WRC is 22lbs/cu foot which yields .4584 lbs per square foot. That makes for hull weight (pre glass, epoxy etc) for 1/4" WRC of 29.79lbs (65 sq.ft. x .4584). You'll be sanding some of this off of course but this is fine for comparison purposes.
If you go to 3/16" strips, the cedar will weigh .3438lbs/sq ft. which yields a hull of 22.34lbs. That is a savings of 7.45lbs - which is huge. (hopefully my calculations are correct - I'm sure someone will correct me if I'm wrong though). You'll have to find out the exact square footage of the freedom to calculate your exact weight savings. If you just went with the 3/16" strips and still used 6 oz. glass that would be a big step to getting lighter.
If you really cut back on trim (within reason) as Todd suggested, you could easily save another 4-5 lbs. or even more.
If Ted gets the old forum back up in an archive or something, you can search for "Light" Jay Morrison's and others posts on reducing weight using various techniques like one pce gunwales and really down-sized dimensions, very small decks etc.
Hope this helps.
Moonman.
I'd go for the 3/16 strips. I haven't used them yet, I'll be doing so on my second boat - but I have made the calculations. I'm just finishing a winisk with a total square footage of planking at 65 square feet. (the Freedom for all intents and purposes should be about the same). WRC is 22lbs/cu foot which yields .4584 lbs per square foot. That makes for hull weight (pre glass, epoxy etc) for 1/4" WRC of 29.79lbs (65 sq.ft. x .4584). You'll be sanding some of this off of course but this is fine for comparison purposes.
If you go to 3/16" strips, the cedar will weigh .3438lbs/sq ft. which yields a hull of 22.34lbs. That is a savings of 7.45lbs - which is huge. (hopefully my calculations are correct - I'm sure someone will correct me if I'm wrong though). You'll have to find out the exact square footage of the freedom to calculate your exact weight savings. If you just went with the 3/16" strips and still used 6 oz. glass that would be a big step to getting lighter.
If you really cut back on trim (within reason) as Todd suggested, you could easily save another 4-5 lbs. or even more.
If Ted gets the old forum back up in an archive or something, you can search for "Light" Jay Morrison's and others posts on reducing weight using various techniques like one pce gunwales and really down-sized dimensions, very small decks etc.
Hope this helps.
Moonman.
With cedarstrips, the gunnels could probably be built fairly light, since the sides of the canoe will already be fairly rigid compared to other types of construction. On my Huron, I'm going with inwales made of white pine core reinforced with a thin strip of ash on the inside edge. The outwales will be thin ash with an "L" cross section.
The decks can be kept minimal, with a small thwart nearby to add rigidity., where normally a larger deck would do the same.
Hardware often seems to be overkill, thinner bolts if possible.
Minimize epoxy and varnish on the fiberglass, an excess is unneeded weight.
Seat strength can be tested for with the "step test" on the materials - step on it and if it doesn't break, it's strong enough. Lightweight fabrics or rawhide, snowshoe style.
Consider a light but tough and abrasion-resistant polyurethane paint (eg.Endura) instead of many coats of varnish for the outside of the hull.
I'm weighing my Huron as I go to track the weight gain - my goal is under 50 pounds, with reasonable strength... good luck with yours.
PS.... about Light Jay's boats, I believe he damaged one on a trip running some rapids... IMO, a really lightweight cedarstrip won't be able to take too much banging around. My Huron will definitely be banged at some time, so fifty pounds seems reasonable, with what I hope will be adequate strengh... anyway, time will tell, and repairs and reinforcements can be made.
The decks can be kept minimal, with a small thwart nearby to add rigidity., where normally a larger deck would do the same.
Hardware often seems to be overkill, thinner bolts if possible.
Minimize epoxy and varnish on the fiberglass, an excess is unneeded weight.
Seat strength can be tested for with the "step test" on the materials - step on it and if it doesn't break, it's strong enough. Lightweight fabrics or rawhide, snowshoe style.
Consider a light but tough and abrasion-resistant polyurethane paint (eg.Endura) instead of many coats of varnish for the outside of the hull.
I'm weighing my Huron as I go to track the weight gain - my goal is under 50 pounds, with reasonable strength... good luck with yours.
PS.... about Light Jay's boats, I believe he damaged one on a trip running some rapids... IMO, a really lightweight cedarstrip won't be able to take too much banging around. My Huron will definitely be banged at some time, so fifty pounds seems reasonable, with what I hope will be adequate strengh... anyway, time will tell, and repairs and reinforcements can be made.